Commentary Purg XVII 91-92

The given of Virgil's whole speech is the universality of love.  It proceeds from God in all His creation, and from all things that He has created.  In the rational beings (angels and humans), it returns to Him; in the lower animals, to one another and to their habitat; in insentient bodies, to their habitat (e.g., water lilies on ponds) or place of origin (e.g., fire always wanting to reach the sky beneath the moon).  See Conv.III.iii.2-5, a passage cited by Singleton (DDP Singleton.Purg.XVII.91-92).